Friction welder

ABSTRACT

A friction welding machine has a direct center drive means wherein the rotor of the drive means functions as the workpiece holding spindle for one or more center driven workpieces; the machine is adapted for use as a dual welder wherein a movable tailstock is employed on each side of the center drive means and also for use with a single tailstock on one side of the center drive and a supplemental thrust bearing means on the other side of the center drive. One embodiment of the machine incorporates a free-floating center drive means. A special workpiece holding device is also provided wherein a special adjustable toggle linkage arrangement is adapted to provide gripping means for a large number of variously sized workpieces.

United States Patent [72] Inventors DaleW.Hollenberg Rolla, Mo.; CalvinD. Loyd, Peoria; Ronald L. Satzler, Metamora, Ill. [21] Appl. No.799,049 [22] Filed Feb. 13, 1969 [45] Patented Oct. 19, 1971 [73]Assignee Caterpillar Tractor Co.

Peoria, Ill.

[5 4] FRICTION WELDER 16 Claims, 12 Drawing Figs.

[52] US. Cl 228/2, 29/4703, 156/73, 279/41 [51] Int. Cl B231: 27/00 [50]Field of Search 228/2;

[5 6] References Cited UNITED STATES PATENTS 3,417,457 12/1968Burkeetal. 29/4703 Primary Examiner.lohn F. Campbell AssistantExaminerRobert J. Craig AnorneyFryer, Tjensvold, Feix, Phillips & LempioABSTRACT: A friction welding machine has a direct center drive meanswherein the rotor of the drive means functions as the workpiece holdingspindle for one or more center driven workpieces; the machine is adaptedfor use as a dual welder wherein a movable tailstock is employed on eachside of the center drive means and also for use with a single tailstockon one side of the center drive and a supplemental thrust bearing meanson the other side of the center drive. One embodiment of the machineincorporates a free-floating center drive means. A special workpieceholding device is also provided wherein a special adjustable togglelinkage arrangement is adapted to provide gripping means for a largenumber of variously sized workpieces.

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D W v L v A0 9/ CR FRICTION WELDER BACKGROUND OF THE INVENTION Thisinvention relates to improvements in friction welding apparatus of thegeneral type wherein two workpieces are subjected to relative rotationwhile in contact with each other to generate frictional heat to raisethe workpieces to a suitable welding temperature, whereupon the relativerotation subsides and a bond is formed between the workpieces.

It is also to be understood that the invention is specificallyapplicable to apparatus for performing the inertia welding process asdescribed in US. Pat. No. 3,273,233 and as set forth below. In theinertia welding process the energy required to bring the commoninterface of the parts to a bondable condition is stored as kineticenergy in rotating inertia weights. These weights generally take theform of flywheels and are connected to one of the parts and the entireenergy necessary to form the bond is stored in the weights prior to theengagement of the parts at the interface. The stored energy isdischarged into the interface through frictional heating and plasticworking developed at the interface as the rubbing contact slows therotating weights and the bonding cycle is concluded.

More specifically, the present invention is directed to a frictionwelding machine having a direct center drive means wherein the rotor ofthe drive means functions as the workpiece holding spindle for one ormore center driven workpieces. Use of the rotor shaft as the welderspindle offers important advantages over prior art structures in that itprovides a drive system which eliminates the use of costly gearingarrangements, complicated belt drives and pulleys, etc. The eliminationof such intermediate drive components also reduces lubricationrequirements as well as maintenance problems associated with therelatively complex drive systems of prior art devices.

A further object and advantage of the invention resides in theemployment of a center drive workpiece holding device which in oneembodiment comprises a free-floating center drive and wherein either asingle workpiece may be held in and protrude from either end of thecenter drive, or separate workpieces may protrude from either end of thecenter drive, and a tailstock assembly is provided on either side of thecenter drive means for holding separate workpieces against rotation andwherein the tailstock assemblies may be simultaneously actuated to moveaxially into engagement with the center drive means whereby axial thrustforces are balanced at the center drive means.

A further object and advantage of the friction welding device of thepresent invention resides in the employment of either a fixed directcenter drive or a free-floating center drive means in combination with amovable tailstock on one side of the center drive and a supplementalthrust bearing means on the other side of the center drive.

Still another object and advantage of the invention resides in theprovision of a workpiece holding device having an adjustable togglelinkage arrangement to permit clamping and accurate adjustment forvarious sizes of workpieces.

Other and further objects and advantages of the present invention willbe apparent from the following description and claims and areillustrated in the accompanying drawings which, by way of illustration,show preferred embodiments of the present invention and the principlesthereof and what are now considered to the be the best modescontemplated for applying these principles. Other embodiments of theinvention embodying the same or equivalent principles may be used andstructural changes may be made as desired by those skilled in the artwithout departing from the present invention and the purview of theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational viewillustrating one exemplary embodiment of a friction welding machineconstructed in accordance with the present invention;

FIG. 2 is a top plan view of the friction welding machine shown in FIG.1;

FIG. 3 is a cross-sectional view taken on the line III-III of FIG. l andillustrating certain details of the center drive means of the presentinvention;

FIG. 4 is a longitudinal view, partially in section, illustratingcertain structural details of the center drive means of the presentinvention;

FIG. 5 is a cross'sectional view illustrating structural details of anovel workpiece holdingdevice of the present invention;

FIG. 6 is a top plan view of the workpiece holding device depicted inFIG. 5;

FIG. 7 is an end view of a friction welding machine constructed inaccordance with the present invention;

FIG. 8 is a side elevational view illustrating a modified em bodiment ofa friction welding machine constructed in accordance with the presentinvention and including a free-floating center drive means;

FIG. 9 is a cross-sectional view taken on the line IX-IX of FIG. 8 andillustrating certain details of the free-floating center driveembodiment of the present invention;

FIG. 10 is a side elevational view illustrating a modified embodiment ofthe friction welding machine shown in FIG. 8;

FIG. 11 is a longitudinal view, partially in section, illustratingcertain structural details of a supplemental thrust bearing arrangementfor use with the embodiment illustrated in FIG. 10; and

FIG. 12 is an end view of the supplemental thrust bearing arrangementillustrated in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT A friction welding machineconstructed in accordance with one exemplary embodiment of the presentinvention is indicated generally by the reference numeral 10 in FIGS. 1and 2. The welding machine 10 comprises a housing or frame 12 whichhouses suitable hydraulic controls 14 and electrical controls 16 for theoperation of the machine as will be described at a later point in thedescription. A heat exchanger unit 17 is provided at one side of theframe to provide oil cooling for various parts of the machine in theevent such cooling is found necessary or desirable. The top of thehousing 12 is provided with a bed plate 18 for supporting variouscomponents of the welding machine.

Guide means, preferably in the form of a pair of spaced guide rods 20are supported on the bed 18 by means of suitable mounting brackets 22. Ahollow shaft, electrical induction, drive motor shown generally at 24 isfixedly supported upon the guide rods 20 by means of a gusset and standassembly 25 which is secured at its lower end to the bed plate 18. Aswill be described in detail at a later point of the description a hollowrotor shaft of the motor 24 serves as the center drive spindle forrotating one or more workpieces to be welded such as shown at 26 and 28.

Two movable tailstocks shown generally at 30 and 32 are slidablysupported upon the guide rods 20 on each side of center drive motor 24.A pair of double-acting hydraulic rams 34 are rigidly mounted to the endsupport brace 22 with their rod ends extending through the support forattachment to tailstock 30 as shown at 35. A similar pair of rams 36 areprovided for movement of the tailstock assembly 32. While two rams areshown associated with each tailstock, it is to be understood thatunitary ram means could be employed if desired. The rams 34 and 36 areprovided with a fluid pressure port 37 for the admission and emission ofpressure fluid from the hydraulic controls to the head ends of the rams.A similar fluid pressure port 38 is provided for the rod ends of therams.

As best shown in FIG. 3 the center drive motor is fixedly secured to theguide bars 20 by means of cantilever clamps 27. During a frictionwelding operation the tailstock assemblies 30 and 32 are simultaneouslyactuated by the rams 34 and 36 to engage workpieces (not shown) held inthe tailstocks with the rapidly rotating workpieces 26 and 28 held in.the center drive 24.

Referring now to FIG 4 in conjunction with FIG. 3, it will be observedthat the motor 24 comprises stator windings 46 which are embedded inslots provided in the stator core 48. Rotor bars 50 are shown embeddedin the slots provided in the rotor core 52. The rotor and stator areseparated by a radial airgap 54.

It should be noted that a spindle or rotor shaft 56 is provided with ahollow bore 58 through which a center driven workpiece or workpieces canbe inserted to be clamped by chucks 60 and 62 attached at either end ofthe rotor shaft 56. Since the core through the rotor shaft is coaxialwith the chuck openings one long workpiece can be passed through therotor to be clamped by both chucks or each of two shorter workpieces canbe held in the individual chucks.

The rotor shaft is also provided at either end with flange elements 64.The flange elements 64 are provided with drilled holes or other suitablemeans for attaching the chucking devices 60 and 62 and also one or moreflywheels such as 66 which may be required to provide the proper amountof stored energy. Suitable bearing means 67 are provided for the shaftassembly 56.

The motor 24 is a Class K induction motor which is a low slip device.The Class K motor is characterized by low torques at speeds that are alow percentage of synchronous speed but develop maximum torque at aboutcycles of slip from synchronous speed regardless of the frequencyapplied to the motor. Maximum motor efiiciency (electrical) is at aboutone cycle slip. These characteristics used in a variable frequencysystem allow the advantage of a highly efficient system over ahigh-speed range.

The details of the tailstock assembly 30 will now be described withreference to FIGS. 5, 6 and 7. It should be understood that thedescription with respect-to the tailstock 30 applies equally to thetailstock 32. As best shown in FIGS. 5 and 6 a tailstock frame comprisestwo laterally spaced end plates 80 and 80' reinforced by a bottom plate82 and two connecting metal straps 84 and 86. The end plates are furtherconnected by tubular bushings 88 and the tailstock is slidably mountedon the guide rods through the employment of linear motion bearings 90.

First toggle links 92 and 92' are secured in the tailstock bythrough-bolts 94 and 94' as best shown in FIG. 6. The toggle links 92and 92' extend the full length of the tailstock and have three projectedconnecting arms 96, 98 and 100. A second set of toggle links 101 and 102are connected to the first set of toggle links by pins 104 and 106respectively. The second set of toggle links 101 and 102 are providedwith V- blocks 108 and 110 which are attached to the ends of the links101 and 102 respectively, such as by countersunk capscrews.

The center arms 98 and 98' formed on the first toggle links 92 and 92'are pivotally connected by pins Ill and 111'to the upper ends ofactuating links 112 and 114. The lower ends of actuating links 112 and114 are connected by a common pivot pin 115 to the bifurcated end ofarod 116. The rod 116 is provided with a piston 117 which is received ina cylinder 118. The cylinder 118 is mounted to the center of bottomplate 82 and the rod 116 extends upwardly through the bottom plate tothe pivotal attachment 115 for the actuating links 112 and 114.

Actuation of the above-described double-toggle arrangement to causeclamping and unclamping of a workpiece is effected by vertical motion ofthe rod 116 inwardly and outwardly of the cylinder 118. Thus, when oilis introduced at a port 126 the rod 116 will be moved inwardly as shownand the V-blocks 108 and 110 will be moved into a clamped position.Introducing pressure fluid at a port 128 will cause the rod 116 to bemoved outwardly of the cylinder 118 and thereby move the V-blocks 108and 110 to an unclamped position.

The V-blocks 108 and 110 are replaceable to permit the clamping ofvarious sized workpieces. Further, an are traced by the links 101 and102 is adjustable to cause the V-blocks 108 and 110 to engage theworkpiece properly. Adjustment of the aforementioned arc is accomplishedby follower elements, such as small rollers or pins 134 and 136 mountedon the links 101 and 102, following a path defined by arcuate guides 138and 140.

The position of the arcuate guides 138 and 140 is adjustable throughpositioning of rods 142 and 144 associated with each of the guides 138and 140. The rods 142 and 144 are welded to the guides 138 and 140 andvertical adjustment of the guides is provided through adjustment nutsand 151 associated with the rod 142, and nuts 152 and 153 associatedwith the rod 144. Transverse adjustment of the guides 138 and 140 isprovided by slots 154 and 155 formed in the metal straps 84 and 86 andslots 156 formed in the bottom plate 82.

Prior to clamping the workpiece in the V-blocks 108 and 110, theworkpiece is placed in a bracket 160 which holds the workpiece at thecorrect level prior to being clamped by the V-blocks. The brackets 160are replaceable and can be changed with the V-blocks to permit weldingof various sized parts.

The hydraulic control 14 of FIG. 1 consists of a fluid source, pressurepump, and other components to permit proper operation of the tailstockcylinders 118 and the thrust rams 34 and 36. The electrical controls 16comprise proper circuitry to start and accelerate the motor 24 to apreselected speed, sense the motor speed, automatically shutoff power tothe motor when a speed is proper and provide a signal to the hydrauliccontrols to initiate the welding sequence.

At the beginning of a welding operation either a single workpiece may befed through the hollow shaft of the motor 24 and clamped in place byclosing chucks 60 and 62 or two separate workpieces may be clamped inthe chucks 60 and 62. Separate workpieces are then placed in each of thetailstock assemblies 30 and 32 and the hydraulic controls 14 areactuated to cause tailstock cylinders 118 to lock the workpiecessecurely in the tailstocks.

The electrical controls are then set and actuated to cause the motor 24to accelerate to a speed proper for welding of the materials beingjoined. When the desired speed is reached, a feedback speed signalcauses the power to the motor to be discontinued and simultaneously asignal is sent to the hydraulic controls to supply pressure fluid torams 34 and 36 which causes the tailstocks 30 and 32 to be urged towardthe motor 24 until the workpieces held in the tailstocks come intocontact with the rotating workpiece or workpieces held in the spindle ofthe motor 24.

During the welding operation the fixed motor 24 is in a balancedcondition between the tailstocks 30 and 32 since the thrust of the rams34 cancels out the thrust of the rams 36. This balanced conditionminimizes the load on the bearings of the motor 24. Upon completion ofthe weld, the controls function to operate the tailstock cylinders 118to unclamp the workpieces and the chucks 60 and 62 are loosened topermit the joined workpieces to be removed.

In the event that a single workpiece is fed through the hollow shaft ofthe motor 24 and welded to end pieces held in each of the tailstockassemblies 30 and 32, the joined material may be fed through the welderuntil the free end of the part originally held in one of the tailstocksis located in the other tailstock. If desired a new splice section canthen be inserted through the motor and a new long workpiece sectionclamped in the now vacant tailstock to permit repetition of theabovedescribed process. This latter procedure would be especiallybeneficial for rod or wire splicing wherein the joined sections areeventually formed in a large coil.

FIG. 8 illustrates a modified embodiment of the invention wherein thedrive motor is free-floating or slidably supported on the guide rodsrather than being fixedly secured thereto as shown in the embodiment ofFIGS. 1 and 2. Those portions of the machine shown in FIG. 8 which areidentical with the machine 10 of FIGS. 1 and 2 carry the same referencenumeral with a prime symbol added.

FIG. 8 illustrates a free floating, hollow shaft, electrical induction,drive motor, shown generally at 24, slidably supported upon the guiderods 20'. FIG. 9 is a cross-sectional view ofthe motor 24' taken on theline lX-IX of FIG. 8.

As shown in FIG. 9 the motor housing 40 is provided at each side withtubular extensions 42 which are preferably formed integrally with themotor housing 40. The guide rods 20' are shown disposed in the bores ofthe tubular members 42 which are mounted over the guide rods through theemployment of linear motion bearings 44.

Due to this hearing arrangement, during a welding operation the centerdrive motor 24' floats upon the guide bars 20' and the tailstockassemblies 30' and 32' are simultaneously actuated by the rams 34' and36' to engage workpieces (not shown) held in the tailstocks with rapidlyrotating workpieces held in the center drive motor. It should beunderstood that during the welding operation the free-floating motor 24'is balanced in a position between the 'tailstocks 30' and 32 since thethrust of the rams 34' cancels out the thrust of the rams 36'.

FIG. illustrates a modified embodiment of the invention shown in FIG. 8wherein a free-floating center drive friction welder is adapted to makea single weld rather than two welds. When making dual welds (one at eachend) with a free-floating center drive motor (as in FIG. 8) very littlethrust is transmitted to the bearings of the center drive spindle.However, when making a single weld at one end of the free-floatingcenter drive welder, provision must be made to locate the spindle topermit thrust loading at the weld interface and relieve the spindlebearings of thrust loads which might exceed their designed thrustresistance. As will be described in greater detail below, the embodimentof FIG. 10 employs a supplemental thrust bearing arrangement 199 tocounteract thrust loading at the interface of a single pair of weldmembers disposed at one end of the machine. The thrust unit is alow-inertia device to minimize its influence on the deceleration rate ofthe spindle.

Those portions of the machine shown in FIG. 10 which are identical withthe machine 10' shown in FIG. 8 carry the same reference numeral. Asshown in FIG. 10 the thrust rams 34, tailstock assembly 30 etc., to theleft of the free-floating drive motor 24' remain as describedpreviously. The tailstock assembly to the right of the drive motor isnot shown, and in fact may preferably be removed from the machine whenperforming a single weld operation.

The drive motor in FIG. 10 is free-floating on the tie bars and thesupplemental thrust bearing means 199 are provided for limiting movementof the motor to the right so that the thrust rams 34' can provideadequate thrust loading at the interface of the weld members held intailstock and rotating chuck 60. In addition the supplemental thrustbearing means 199 should operate to effectively prevent damaging thrustloads from being transmitted to the spindle bearings of drive motor 24.

Referring now to FIG. I0 in conjunction with FIG. 11 the flange element64' at the right of spindle 56 has nothing attached to it and ispreferably provided with a friction face 65. The supplemental thrustbearing means 199 comprises a flange 200 which is also provided with afriction face 202 adapted for frictional engagement with the frictionface 65 of flange 64' during a welding operation. The flange element 200is secured by bolts to a rotatable shaft 204 which is adapted forlimited longitudinal movement in a chamber 206 defined by a housing 208.As shown in F IG. 12 the housing 208 is fixedly clamped to the tie bars20 by bolted clamp elements 209.

A suitable sealing element, such as a labyrinth seal shown generally at210 insures a fluidtight connection where the shaft 204 enters thehousing 208. A fluid passageway 212 leads away from the seal 210 to adrain conduit 214. A first roller bearing element 216 is providedbetween a shoulder 218 on the shaft 204 and an annular retainer ring 220secured to the housing 208. A second and similar bearing element 222 isprovided between the shaft 204 and the wall of cavity 206 and is held inplace between an annular shoulder 224 and a snap ring 226.

The cavity 206 is provided with a reduced diameter portion 220 intowhich the end 230 of the shaft 204 projects in a pistonlike manner.Preferably, the reaction surface of the shaft end 230 is equal to thereaction surfaces associated with the thrust rams 34. A very smallannulus 232 is provided between the shaft end 230 and the wall ofreduced diameter cavity 228 to provide a controlled fluid leakage pathout of reduced cavity 228 into main cavity 206. A pressure fluid inletport is provided at 234 for the admission of pressure fluid during awelding operation as will be described below.

A welding operation of the device shown in FIGS. 10 and 11 is carriedout as follows. Assuming that free-floating motor 24' is rotating at theproper speed the hydraulic controls 14' are actuated which suppliesfluid to the tailstock rams 34 and the stationary workpiece held in thetailstock chuck is advanced along the guide bars 20' toward the rotatingworkpiece held in chuck 60'. Simultaneously fluid pressure is admittedthrough the port 234 to the cavity 228 of the supplemental thrust means199.

After the weld pieces come into contact the motor 24 will moverightwardly under the thrust from rams 34 until the flange element 64comes into contact with flange element 200 of the shaft 204. The shaft204 will now begin rotating and a hydrostatic thrust bearing will beestablished between shaft end 230 and cavity 228 to offset the thrustapplied by the tailstock rams 34'. Since the thrust loading imposed byrams 34 is counteracted by the hydrostatic bearing established in member199 no appreciable amount of thrust load is exerted on the bearings ofmotor 24'.

The supplemental thrust bearing means 199 of FIGS 10, 11 and 12 has beenillustrated as a hydrostatic thrust bearing unit. However, it is to beunderstood that other suitable thrust bearing elements could beutilized. The only requirements for such a thrust bearing unit are thecapability of permitting free rotation for the thrust shaft 204 andsimultaneously absorbing the thrust from rams 34' so that this thrustforce does not damage the motor bearings which permit rotation of themotor shaft 56.

It should also be understood that a supplemental thrust bearing meanssimilar to the unit at 199 could be used with the fixed center driveembodiment of FIGS. 1 and 2 when that embodiment is adapted to make asingle weld rather than two welds. The supplemental thrust assembly 199could be installed on the guide rods 20 with the friction surfaceabutting the motor flange to relieve thrust loads imposed on the motorbearings when making welds at only one end of the center drive 24.

While we have illustrated and described preferred embodiments of ourinvention, it is to be understood that these are capable of variationand modification, and we therefore do not wish to be limited to theprecise details set forth, but desire to avail ourselves of such changesand alterations as fall within the purview of the following claims.

l. A friction welding machine comprising:

a main frame;

guide means extending longitudinally of the frame;

a single center drive means mounted on the guide means centrally of themachine frame;

said center drive means comprising a motor having a rotor; a workpieceholding spindle rigidly connected to the rotor and projecting outwardlyfrom each side of the rotor;

spindle chuck means rigidly mounted on the spindle for holding a spindleworkpiece for rotation with said rotor during engagement of the spindleworkpiece with tailstock workpieces at the ends of the spindle;

a pair of tailstock assemblies mounted for sliding movement on the guidemeans on either side. of the center drive means, each tailstock havingtailstock chuck means for holding a tailstock workpiece againstrotation; loading means connected to each of the tailstock assembliesfor moving the tailstock assemblies inwardly toward the motor to pressthe two tailstock workpieces against the spindle workpiece;

and wherein the rigid connection between the rotor and spindle chuckmeans utilizes all of the kinetic energy of the decelerated motor rotoras the two welds are produced with the tailstock workpieces at the endsof the spindle.

2. A friction welding machine as set forth in claim 1 wherein the centerdrive means is fixedly secured to the guide means to prevent movementthereof.

3. A friction welding machine as set forth in claim 1 wherein the centerdrive means is slidably mounted on the guide means for free-floatingmovement thereon.

4. A friction welding machine as set forth in claim 1 wherein said guidemeans comprises at least two tie bars extending longitudinally of themachine frame.

5. A friction welding machine as set forth in claim 1 wherein said rotorcomprises an electrical motor.

6. A friction welding machine as set forth in claim 5 wherein said rotorcomprises an electrical induction motor.

7. A friction welding machine as set forth in claim 1 wherein said rotorcomprises a hollow shaft.

8. A friction welding machine as set forth in claim 1 wherein saidcenter drive rotor is provided with a workpiece holding chuck on eachend thereof; said machine further comprising, ram means for axiallymoving each tailstock on the guide means towards the center drive means;and means for simultaneously actuating the rams to move the workpiecesheld by each tailstock into engagement with the workpieces held at eachend of the center drive motor, whereby axial thrust loads exerted by therams produce a balanced condition at the center drive means.

9. A friction welding machine as set forth in claim 8 wherein said guidemeans comprise at least two tie bars extending longitudinally of themachine frame and said motor comprises an electrical motor.

10. A friction welding machine as set forth in claim 8 wherein saidrotor comprises a hollow shaft.

11. A friction welding machine as set forth in claim 9 wherein saidrotor comprises a hollow shaft.

12. A friction welding machine comprising a main frame; guide meansextending longitudinally of the frame; a drive means for rotating afirst workpiece relative to a second workpiece, said drive meansbeingcentrally mounted for free floating movement longitudinally on theguide means; said drive means including a motor, a rotor in the motor, aspindle rigidly connected to the rotor, spindle chuck means for holdingsaid first workpiece for rotation with the spindle and rotor, andbearing means for permitting rotation of the rotor and spindle withinthe motor housing; a tailstock assembly mounted for sliding movement onthe guide means on a first side of the drive means and having means forholding a second workpiece; loading means for axially moving saidtailstock assembly along the guide means to engage said first and secondworkpieces, and a separate thrust bearing means, located externally ofthe drive means on a second side of said center drive means, forabsorbing axial thrust forces transmitted through said free-floatingdrive means during engagement of said first workpiece with said secondworkpiece; whereby the maximum axial forces to which the spindle bearingmeans are subjected during a weld cycle are of a very low magnitude.

13. A friction welding machine as set forth in claim 12 wherein saidthrust bearing means comprises a hydrostatic bearing assembly.

14. A friction welding machine as set forth in claim 12 wherein saidguide means comprises at least two tie bars extending longitudinally ofthe frame.

15. A friction welding machine as set forth in claim 12 wherein saidmotor comprises an electrical induction motor.

16. A friction welding machine as set forth in claim 12 wherein saidrotor shaft is hollow.

Patent No.

Inventor(s) (SEAL) Attest:

Attesting Officer EDWARD M.FLETCHER,JR.

UNITED STATES PATENT OFFICE Dated October 19, 1971 and Galvin D1 Lovd Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

The original patent identified above carries the number 3,613,982 on thecover and the typewritten specification and claims, whereas all eightsheets of the drawings are identified with the incorrect number Signedand sealed this 22nd day of August 1972.

ROBERT GOTTSCHALK Commissioner of Patents ORM PO-IOSO (10-63) USCOMM-DCGOING-P69 s u s covznnmsm' Pmmmu OFFICE 1 $969 0-300-334

1. A friction welding machine comprising: a main frame; guide means extending longitudinally of the frame; a single center drive means mounted on the guide means centrally of the machine frame; said center drive means comprising a motor having a rotor; a workpiece holding spindle rigidly connected to the rotor and projecting outwardly from each side of the rotor; spindle chuck means rigidly mounted on the spindle for holding a spindle workpiece for rotation with said rotor during engagement of the spindle workpiece with tailstock workpieces at the ends of the spindle; a pair of tailstock assemblies mounted for sliding movement on the guide means on either side of the center drive means, each tailstock having tailstock chuck means for holding a tailstock workpiece against rotation; loading means connected to each of the tailstock assemblies for moving the tailstock assemblies inwardly toward the motor to press the two tailstock workpieces against the spindle workpiece; and wherein the rigid connection between the rotor and spindle chuck means utilizes all of the kinetic energy of the decelerated motor rotor as the two welds are produced with the tailstock workpieces at the ends of the spindle.
 2. A friction welding machine as set forth in claim 1 wherein the center drive means is fixedly secured to the guide means to prevent movement thereof.
 3. A friction welding machine as set forth in claim 1 wherein the center drive means is slidably mounted on the guide means for free-floating movement thereon.
 4. A friction welding machine as set forth in claim 1 wherein said guide means comprises at least two tie bars extending longitudinally of the machine frame.
 5. A friction welding machine as set forth in claim 1 wherein said rotor comprises an electrical motor.
 6. A friction welding machine as set forth in claim 5 wherein said rotor comprises an electrical induction motor.
 7. A friction welding machine as set forth in claim 1 wherein said rotor comprises a hollow shaft.
 8. A friction welding machine as set forth in claim 1 wherein said center drive rotor is provided with a workpiece holding chuck on each end thereof; said machine further comprising, ram means for axially moving each tailstock on the guide means towards the center drive means; and means for simultaneously actuating the rams to move the workpieces held by each tailstock into engagement with the workpieces held at each end of the center drive motor, whereby axial thrust loads exerted by the rams produce a balanced condition at the center drive means.
 9. A friction welding machine as set forth in claim 8 wherein said guide means comprise at least two tie bars extending longitudinally of the machine frame and said motor comprises an electrical Motor.
 10. A friction welding machine as set forth in claim 8 wherein said rotor comprises a hollow shaft.
 11. A friction welding machine as set forth in claim 9 wherein said rotor comprises a hollow shaft.
 12. A friction welding machine comprising a main frame; guide means extending longitudinally of the frame; a drive means for rotating a first workpiece relative to a second workpiece, said drive means being centrally mounted for free floating movement longitudinally on the guide means; said drive means including a motor, a rotor in the motor, a spindle rigidly connected to the rotor, spindle chuck means for holding said first workpiece for rotation with the spindle and rotor, and bearing means for permitting rotation of the rotor and spindle within the motor housing; a tailstock assembly mounted for sliding movement on the guide means on a first side of the drive means and having means for holding a second workpiece; loading means for axially moving said tailstock assembly along the guide means to engage said first and second workpieces, and a separate thrust bearing means, located externally of the drive means on a second side of said center drive means, for absorbing axial thrust forces transmitted through said free-floating drive means during engagement of said first workpiece with said second workpiece; whereby the maximum axial forces to which the spindle bearing means are subjected during a weld cycle are of a very low magnitude.
 13. A friction welding machine as set forth in claim 12 wherein said thrust bearing means comprises a hydrostatic bearing assembly.
 14. A friction welding machine as set forth in claim 12 wherein said guide means comprises at least two tie bars extending longitudinally of the frame.
 15. A friction welding machine as set forth in claim 12 wherein said motor comprises an electrical induction motor.
 16. A friction welding machine as set forth in claim 12 wherein said rotor shaft is hollow. 